The invention relates generally to hand-held, dual bit drills and more specifically to an adjustable, hand-held, dual bit drilling machine having an expandable positioning collet or locating pin and components for providing an automatic operating sequence.
The precision drilling of blind or through openings in metal involves many parameters. Those that may be characterized as basic or fundamental include opening location, that is, its position on the X-Y plane of the workpiece surface and the nominal diameter of the opening. Other less apparent but equally important parameters include the opening shape, i.e., its circularity or lack thereof, the surface smoothness of the opening and the axial orientation thereof. Satisfying these parameters and others becomes a complex problem when more than one opening is drilled simultaneously due to interaction between the drills, the workpiece and the drilling equipment.
Significant attention has been addressed to resolving the difficulties attendant drilling openings in workpieces. For example, U.S. Pat. No. 2,847,881 teaches a drilling machine having locating pins which translate with and in advance of the drill bit to engage the workpiece prior to the commencement of a drilling operation. Electrical contacts sense whether proper locating pin motion, which indicates that the workpiece has been properly engaged, has occurred. U.S. Pat. No. 4,061,437 discloses a similar drilling apparatus having a pair of extendable pins which locate a workpiece prior to the engagement of the workpiece by a plurality of compressed air powered drills and the subsequent drilling thereby.
In U.S. Pat. No. 4,197,645, a multiple drill bit dental drill is disclosed. The multiple dental drills are closely spaced and rotate in opposite directions with the cutting surfaces of each drill overlapping the cutting surfaces of at least one adjacent drill.
U.S. Pat. No. 4,729,230 teaches a multiple spindle drilling machine having a drilling head which carries a plurality of drilling spindles. The drilling head is located by a pair of positioning pins which are moveable relative to the drilling head.
In U.S. Pat. No. 4,898,962, a portable positive feed drill is disclosed which includes a drill spindle and lead screw coupled to and commonly driven by a gear train. A pair of guides couple a work engaging foot to the housing of the drill. A depth of cut adjustment includes pairs of jam nuts disposed on a threaded shaft.
In U.S. Pat. No. 4,897,000, a clamping apparatus for drilling and countersinking holes in a workpiece is illustrated. The apparatus is utilized for countersinking rivet holes in airplane fuselages and includes a cantilevered arm for insertion in the fuselage. The arm includes a fluid cylinder and motor which is coupled to an anvil. These components are in turn coupled to a rotary actuator which may revolve the anvil assembly to an angle of at least 180.degree..
In order to properly locate the drill bit on the X-Y plane surface of the workpiece, an expandable collet has been utilized to position and hold the drilling machine and thus the drill bit in a fixed position relative to a previously drilled opening or locating aperture.
In U.S. Pat. No. 4,963,927, a pair of tandem, double acting pistons and cylinders are utilized to move a mandrel disposed in a collet in order to expand the collet. By selectively pressurizing the cylinders, the cylinder housing and collet mandrel translate up or down and into an engaged or disengaged position, as desired.
U.S. Pat. No. 3,599,958 teaches a collet expanding mechanism for use with a drill or similar machine wherein the collet mandrel is coupled to a direct acting air cylinder by a first class lever.
A similar device is disclosed in U.S. Pat. No. 3,663,115. This patent teaches another linkage between a double-acting pneumatic cylinder and the mandrel of a work and drill positioning collet. A pivot lever arm having a roller which contacts a ramp on the piston rod provides axial motion to the collet mandrel and expands and releases the collet.
The difficulties of single drill positioning and control are complicated when it is desired to drill multiple apertures. Significant attention has been paid to the solution of problems relating to this specific drilling task as well. For example, the device disclosed in U.S. Pat. No. 2,909,949 is a hand-held twin drill device having an expandable drill positioning collet. The axial positions of the drill bits are individually adjustable. The spacing between the axes of the drill bits is not readily adjustable.
Adjustment of the spacing between the axes of a pair of drills is, however, adjustable in U.S. Pat. No. 3,652,175. Here, the use of shaft couplings to permit shaft movement along a line of action perpendicular to the drill bit axis is disclosed.
In U.S. Pat. No. 4,286,902, a drill mechanism similar to that illustrated in U.S. Pat. No. 2,909,949 is disclosed. This drill, however, permits the adjustment of inter-drill spacing. This adjustment may be characterized as a fixed adjustment inasmuch as the removal and replacement of one dual shaft drive assembly by another having different spacing is the mode of adjusting such drill axis spacing. The axial position of each drill bit may also be adjusted by means similar to that disclosed in the '949 patent.
U.S. Pat. No. 4,365,916 also teaches a mechanism for adjusting the position of drills or other machining elements. A cylinder having internal drive components coupled to a spindle is offset from the cylinder axis. Rotation of the cylinder thus repositions the spindle.
In U.S. Pat. No. 4,396,318, a collet-type drill having improved clamping means is disclosed. Again, the collet is expanded by a mandrel operated by a double-acting pneumatic piston.
Finally, U.S. Pat. No. 4,678,378 presents an adjustable drill head attachment for mounting on a dual drill gun or drill press. The drill includes a threaded adjustment mechanism and guide rod.
From the foregoing review of prior art patents, it is apparent that improvements in the art of collet positioned, dual bit drilling machines having adjustments to both the axial drill bit positions as well as the axial inter-drill spacing are both desirable and possible.